The invention relates generally to an arrangement for the automatic wireless transmission of multi-place numerical information between active interrogation devices and passive reply devices which are movable with respect to one another, particularly for track-bound transport apparatus. The respective passive reply devices each utilize a plurality of resonators coupled to a high frequency line section, with the plurality of resonators being proportional to the number of places of the information to be transmitted. The varying resonant frequencies of said resonators determine, in connection with a mutual minimum interval, the wobble range for the interrogation signal transmitted by the interrogation device with a periodic change of frequency, with the interrogation device receiving the signals reflected from the reply device.
More particularly, the invention is directed to a novel construction of a passive reply device and the method of making the same.
Arrangements are known, for example, from German AS 19 01 890 and British Pat. No. 1,496,205 (German LP 24 25 182), in which the individual resonant frequencies are generated by means of resonators, for example quarter-wave coaxial resonators, coupled to a waveguide, said resonators being interrogated by means of a wobbled microwave signal. In this case, the reply device comprises two half-shells which are cooperable to form a rectangular waveguide and an antenna therefor, and further includes coaxial resonators which are integrally cast with the waveguide. In order to achieve favorable mass production costs, significant center frequency errors caused by fabrication tolerances can be expected. This center frequency error is compensated by means of a fundamental equalization. Thus, the informational variation involving different frequencies within a specific frequency range, requires an additional equalization of the resonators. The frequency equalization of the coaxial resonators usually is achieved by the utilization of additional timing elements which are introduced, in an appropriate manner, in the hollow space of the coaxial resonator. Thus, an electrically conductive pin can be inserted through the bottom wall of the resonator (short-circuit plane), whereby an inductive frequency shift results. This method requires a processing of the resonators which, at least in part, involves a significant outlay, namely boring, deburring and smoothing. This operation also involves the danger of a high rejection, since a single bore which is not to precise dimensions can result in the rejection of an entire half-shell. From an electrical standpoint, the use of a pin type equalization results in the further problem that, independently of the size of the frequency deviation, the pin influences the resonator open circuit band width and, thus, also the signal.